Pizza is to Chicago what neon is to Vegas—sure, you’ve seen something with the same name back home, but never as traffic-stoppingly enormous as this. Deep dish pizza is the first thing visitors want to try when they get here, and often the last thing they stuff, frozen, into a suitcase. And happily, many top examples—including the very place where it was invented—are located in the downtown area where visitors are likely to be staying.

By any normal standard, Chicago deep dish pizza is built backwards—the crust is topped with cheese first, then meat, and finally crushed tomatoes are spread over the whole thing. But it’s the layer of spiced, acidic Italian tomatoes on top that make it so robust, a mind-blowing four-course Italian feast in a slice. As Spinal Tap would say, it’s pizza dialed up to 11.

Chicago deep dish was invented in 1943 at Pizzeria Uno, two blocks west of Michigan Avenue on Ohio (there’s a sibling, Pizzeria Due, a block north; choose whichever one has a shorter line). Everyone agrees on that; what they don’t agree on is whether it was invented by owner Ike Sewell or cook Rudy Malnati Sr., whose sons would go on to spawn two other iconic deep dish chains. Lou would start Lou Malnati’s in the 1970s, while Rudy Jr. started Pizano’s Pizza & Pasta a few years later.

They all follow the backwards model, starting with a crispy short dough (biscuit-like) crust that’s nothing like the kind of dough New York pizzerias toss in the air. Pizzeria Uno is the meatiest, with a veritable hubcap of sausage covering the whole pizza; Lou Malnati’s has a buttery crust, while Pizano’s is crispier. (The story is that Mama Malnati devised two different family crust recipes to keep peace in the family when Rudy Jr. started his restaurant.) Both Lou Malnati’s and Pizano’s have locations around downtown and the north side near the hotels and attractions. Oh, and if you’ve had a franchised version of Pizzeria Uno in any other city... you haven’t really had Chicago’s Pizzeria Uno.

So that’s the classic Chicago Deep Dish—but confusingly, it’s not the only thing Chicagoans call deep dish pizza. The name is often also applied to pan pizza, which (like pan pizza anywhere) traces back to things like focaccia bread and Sicilian sheet pizza, in which the toppings go on top of a puffy layer of bread. What’s distinctive to Chicago is the variation on pan pizza invented by Burt Katz, who still runs Burt’s Place up in suburban Morton Grove—again, there’s a thick layer of spicy tomato sauce on top, plus cheese around the edges that caramelizes almost black in the pan. On the north side, you can try this at Pequod’s, which Katz started and later sold.

And then there’s stuffed pizza. In the late 1960s, in another tale of rival invention claims, two local chains, Nancy’s and Giordano’s, both started offering an even thicker than deep dish pizza inspired by an Italian Easter pie called scarciedda. All the usual stuff goes in a bread-like crust, but then gets topped with another crust like a pot pie, plus tomato sauce on top.

The sort-of-unbaked top crust skeeves some noted food writers out, but eating a pizza as thick as a Stephen King book is all in a day’s lunch for Chicagoans. Try it at Giordano’s or Edwardo’s downtown, or The Art of Pizza on the north side, but be prepared to place your order an hour before you’re hungry—a pizza of such epic dimensions takes a lot longer than your usual thin crust.